you'd need springs rated for a 6 cylinder, rather than a 4.sr20det itself is just an engine, it's the gearbox that matters. If you do get a halfcut, you would want to avoid a 4WD gearbox. heh.
I'd say stay away from the nissans. Exhaust is on the incorrect side.
I'd also stay away from any 2.0 L 4 cylinder turbo engines... the vehicle is just too heavy for that type of engine.